A Census of the Circumstellar Disk Populations in the Sco-Cen Complex

TL;DR

This study uses WISE mid-infrared data to catalog circumstellar disks in the Sco-Cen complex, revealing disk fractions across different ages and spectral types, and providing insights into disk evolution around young stars.

Contribution

It presents the largest sample of disks in Sco-Cen, offering new statistical constraints on disk fractions and their dependence on spectral type and age.

Findings

Over 1200 IR excess sources identified, with ~400 new detections.

Disk fraction decreases with age and varies by spectral type.

Low-mass stars retain disks at 20 Myr, indicating prolonged disk lifetimes.

Abstract

I have used mid-infrared (IR) photometry from the Wide-field Infrared Survey Explorer (WISE) to perform a census of circumstellar disks among ~10,000 candidate members of the Sco-Cen complex that were recently identified with data from the Gaia mission. IR excesses are detected for more than 1200 of the WISE counterparts that are within the commonly adopted boundary for Sco-Cen, ~400 of which are newly reported in this work. The richest population in Sco-Cen, UCL/LCC, contains the largest available sample of disks (>500) for any population near its age (~20 Myr). UCL/LCC also provides the tightest statistical constraints to date on the disk fractions of low-mass stars for any single age beyond that of Upper Sco (~11 Myr). For Upper Sco and UCL/LCC, I have measured the disk fractions as a function of spectral type. The disk fraction in Upper Sco is higher at later spectral types, which is consistent with the results for previous samples of candidate members. In UCL/LCC, that trend has become more pronounced; the disk fractions in UCL/LCC are lower than those in Upper Sco by factors of ~10, 5.7, and 2.5 at B7-K5.5, K6-M3.5, and M3.75-M6, respectively. The data in UCL/LCC also demonstrate that the disk fraction for low-mass stars remains non-negligible at an age of 20 Myr (0.09+/-0.01). Finally, I find no significant differences in the ages of disk-bearing and diskless low-mass stars in Upper Sco and UCL/LCC based on their positions in color-magnitude diagrams.